1. Field of the Invention
The present invention generally relates to a thermoelectric device, and more particularly, to a thermoelectric device including nanowire structures.
2. Description of Related Art
In accordance with the miniaturizing tendency of electronic and mechanical components or systems, power supplies for driving such systems have also to be correspondingly spatially miniaturized. For example, personal mobile apparatuses, robot systems, and portable systems such as communication devices and electronic products are getting smaller. Correspondingly, the demand for small power supplies is gradually increasing. As such, a power system having a high power density for substituting conventional batteries is highly desired. Currently developed micro-engine technology, with semiconductor processing, has several technical advantages such as smaller size, higher power density, and compatibility than conventional batteries. However, a micro-engine featured in large ratio of surface area to volume within a small space. Therefore, more heat loss and friction loss occur at the surface of the micro-engine. As such, a thermoelectric power generator utilize for effectively recycling surface heat loss and improving the combustion intensity of the micro-engine.
The power generation principle of thermoelectric device relies upon the thermoelectric effect (also known as Seebeck effect) of a thermoelectric material. According to the thermoelectric effect, a current generated by a temperature difference which between a provided heat source and an ambient temperature. Being a solid state material having no moving part, the thermoelectric device has the advantages of high reliability, long lifespan, and noiselessness. Further, when generating power with waste heat, the thermoelectric device is adapted for reducing the environmental thermal pollution.
A thermoelectric device is a combination of multiple groups of N-type and P-type thermoelectric materials. Each group produce current and electrical energy in accordance with temperature difference along the thermoelectric material. The electrical energy is directly proportional with an area of the thermoelectric material, and is inversely proportional with length of the thermoelectric material. Therefore, a thermoelectric device having a larger area to length ratio outputs more electrical energy. In a modularization design, the interface resistance between the thermoelectric material, the electrically conductive layer and the thermally conductive layer is a very important rule on the system efficiency. In addition, conventional thermoelectric block materials have a restricted area to length ratio due to fabrication. It limited electrical energy output from the thermoelectric device. For realistic application, the output electrical power increase through increase the amount of the thermoelectric modules. The weight and cost of system will increase in the same time, and thus disadvantageously affects the application of the thermoelectric device.